commit acca089617b60d966c96b5b56d6e0c7d27acf2c4
author Eli Friedman <eli.friedman@gmail.com> Tue Sep 13 22:08:16 2011 +0000
committer Eli Friedman <eli.friedman@gmail.com> Tue Sep 13 22:08:16 2011 +0000
tree 35b5053e10e5e2e269a5270e51b316c1f73bceae
parent 91672b3c0306bde8b44f38c541d59cd8422e3f93

Revert r139643 while I look into it; it's breaking selfhost.

llvm-svn: 139648

clang/lib/CodeGen/CGBuiltin.cpp

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 271fe66..0c93ed3 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -900,14 +900,13 @@
   case Builtin::BI__sync_lock_release_8:
   case Builtin::BI__sync_lock_release_16: {
     Value *Ptr = EmitScalarExpr(E->getArg(0));
-    llvm::Type *ElLLVMTy =
+    llvm::Type *ElTy =
       cast<llvm::PointerType>(Ptr->getType())->getElementType();
     llvm::StoreInst *Store = 
-      Builder.CreateStore(llvm::Constant::getNullValue(ElLLVMTy), Ptr);
-    QualType ElTy = E->getArg(0)->getType()->getPointeeType();
-    CharUnits StoreSize = getContext().getTypeSizeInChars(ElTy);
-    Store->setAlignment(StoreSize.getQuantity());
-    Store->setAtomic(llvm::Release);
+      Builder.CreateStore(llvm::Constant::getNullValue(ElTy), Ptr);
+    // FIXME: This is completely, utterly wrong; it only even sort-of works
+    // on x86.
+    Store->setVolatile(true);
     return RValue::get(0);
   }
 

clang/lib/CodeGen/ItaniumCXXABI.cpp

diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index d0ec3eb..cbcc449 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1130,27 +1130,20 @@
   } else {
     // Load the first byte of the guard variable.
     llvm::Type *PtrTy = Builder.getInt8PtrTy();
-    llvm::LoadInst *LI = 
+    llvm::Value *V = 
       Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
-    LI->setAlignment(1);
 
-    // Itanium ABI:
-    //   An implementation supporting thread-safety on multiprocessor
-    //   systems must also guarantee that references to the initialized
-    //   object do not occur before the load of the initialization flag.
-    //
-    // In LLVM, we do this by marking the load Acquire.
-    if (threadsafe)
-      LI->setAtomic(llvm::Acquire);
-
-    IsInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
+    IsInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
   }
 
   llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
   llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
 
+  llvm::BasicBlock *NoCheckBlock = EndBlock;
+  if (threadsafe) NoCheckBlock = CGF.createBasicBlock("init.barrier");
+
   // Check if the first byte of the guard variable is zero.
-  Builder.CreateCondBr(IsInitialized, InitCheckBlock, EndBlock);
+  Builder.CreateCondBr(IsInitialized, InitCheckBlock, NoCheckBlock);
 
   CGF.EmitBlock(InitCheckBlock);
 
@@ -1184,5 +1177,23 @@
     Builder.CreateStore(llvm::ConstantInt::get(GuardTy, 1), GuardVariable);
   }
 
+  // Emit an acquire memory barrier if using thread-safe statics:
+  // Itanium ABI:
+  //   An implementation supporting thread-safety on multiprocessor
+  //   systems must also guarantee that references to the initialized
+  //   object do not occur before the load of the initialization flag.
+  if (threadsafe) {
+    Builder.CreateBr(EndBlock);
+    CGF.EmitBlock(NoCheckBlock);
+
+    llvm::Value *_false = Builder.getFalse();
+    llvm::Value *_true = Builder.getTrue();
+
+    Builder.CreateCall5(CGM.getIntrinsic(llvm::Intrinsic::memory_barrier),
+                        /* load-load, load-store */ _true, _true,
+                        /* store-load, store-store */ _false, _false,
+                        /* device or I/O */ _false);
+  }
+
   CGF.EmitBlock(EndBlock);
 }